Absorption of Light in Fluorescent Dyes


Sidki


Introduction


A fluorophore is a part of a molecule which causes a molecule to be fluorescent. It is a functional group in a molecule which will absorb energy of a specific wavelength and re-emit energy at a different wavelength. When these solutions are illuminated by different light sources, the solutions change colors. Fluorescein, eosin Y, rhodamine B are fluorescent dyes which appear a certain color under direct sunlight but illuminate another color under UV lights. Tonic water fluoresces under a UV light because of the quinine. In this experiment I will find the wavelengths and different colors emmited through these dyes under direct sunlight and UV light. Also i will figure out the amount of absorbed light through each liquid at different wavelengths. The chemistry behind this project is fluorescence, absorbance, transmittance and emission. This lab's purpose to measure the amount of absorbed light in certain fluorescent dyes.

Procedure


First, I put 50 mL of tonic water into a 100 mL beaker. Then I put 1.5 ml of 1% fluorescein solution into another 100 mL beaker and diluted it by adding water up to 50 mL. Then I put 0.5 mL of 1% eosin Y solution into another 100 mL beaker and diluted it by adding ethanol up to 50 mL. Then I put 1 mL of 1% rhodamine B solution into another 100 mL beaker and diluted it by adding water up to 50 mL. I then set these 4 beakers on a white sheet paper in front of a window with direct sunlight. I used a spectroscope to observe each solution to see what colors came through and measured the wavelengths. I then put them in front of a UV light and turned off the classroom lights. I used a spectroscope to see what colors came through and measured the wavelengths. Then I put each solution in small test tubes and used a Spec 20 to measure the absorbance at wavelengths from 340-700 nm.

Results

I got great results in this lab. The colors that were illuminated were expected to be seen in the lab.
Name:
Under Sunlight:
Under UV Light:
Tonic Water
Clear and colorless; 700-400 nm
Sky blue color; 600-470 nm
Fluorescein
Light green color; 650-570 nm
Light green color; 630-510 nm
Eosin Y
Salmon color; 650-480 nm
Bright yellow color; 620-550 nm
Rhodamine B
Violet color; 540-460 nm
Bright orange color; 680-630 nm

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Conclusions


Based on results, the dyes when under direct sunlight had a higher range of wavelengths than when they were under the UV light. Based on the graphs, the fluorescein, eosin Y, rhodamine B stayed constant from 340 to 450. Then the absorption amount increased dramatically but decreased immediately after the wavelength went up 20 nm. The tonic water absorption level was high but at 360 nm it decreased dramatically and stayed constant until 700 nm. The fluorescent dyes like fluorescein, eosin Y, and rhodamine had similar absorption from 340 to 700 nm. However, the tonic water was completely different, which I believe has to do with the fact that the quinine is diluted by more water than the other dyes.

References


Fluorescent Dyes, Flinn Scientific, Inc, Publication No. 10218

Helmenstine, Anne Marie. "Fluorescene and Phosphorescence."2009.